Author
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Tworkoski, Thomas |
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Miller, Stephen |
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Submitted to: HortScience
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 6/19/2001 Publication Date: N/A Citation: N/A Interpretive Summary: In mature fruit orchards weeds are controlled to reduce competition, improve access to trees, and eliminate habitat of crop-damaging insects. Diuron, simazine, and terbacil have been available for nearly thirty years and have been applied repeatedly for weed control in fruit orchards. These herbicides can persist in soil for more than one year and fruit tree roots could be exposed to herbicide residues. Fruit growers in the Appalachian Region of the eastern U.S. may use diuron, simazine, and terbacil alone or in combination and occasional failures of new fruit tree plantings have been attributed to residues from herbicide use in the previous orchard. The objective of this experiment was to determine the effect of past long-term use of different herbicides, applied at different rates and combinations on survival and growth of young apple and peach trees. In general, apple tree growth was not affected but peach tree growth was reduced by some herbicide treatments. The greatest reduction in peach tre growth occurred in plots previously treated with herbicides. The greatest reduction in peach tree growth occurred in plots previously treated with high rates of diuron plus terbacil. This herbicide combination also reduced weed growth the most over 15 years and, consequently, soil organic matter was lowest on these plots. Since time of last herbicide treatment had no effect on apple or peach tree growth, the results indicate that reduced fruit tree growth was a consequence of reduced organic matter rather than residual toxic effects of the herbicides. Technical Abstract: Combinations of diuron, simazine, and terbacil were applied every year over 15 and 16 years to the same plots. 'Ace Spur Red Delicious' apple trees on M.7 rootstock and 'Redhaven' peach trees on Lovell rootstock then were planted one and two years following the last herbicide application. In general, apple tree growth was not affected but peach tree growth was reduced by some herbicide treataments. The greatest reduction in peach tree growth occurred in plots previously treated with 4 kg ha-1 diuron plus 2kg ha-1 terbacil. This herbicide combination also reduced weed growth the most over 15 years and, consequently, soil organic matter was lowest on these plots. Time of last herbicide treatment had no effect on apple or peach tree growth The results indicate that reduced fruit tree growth was a consequence of reduced organic matter rather than residual toxic effects of the herbicides. |
